The present invention relates to electronic devices, and more specifically to electrostatic discharge (ESD) protection of integrated circuits.
Metal-oxide-semiconductor (MOS) devices, such as MOS transistors and MOS capacitors are important components in integrated circuits. Many MOS devices include thin gate dielectrics that are susceptible to ESD induced damage. As the thickness of gate dielectrics scales down in more advanced technologies, the gate dielectrics, such as gate oxide, can rupture at lower voltages. Therefore, protecting gate dielectrics from ESD damage is critical.
It is well known that ESD, especially the Charge-Device Model (CDM) type of ESD, can damage the gate oxide of a MOS device. Although ESD devices can be used to protect the gate oxide, oxide rupture can still occur if the ESD devices have higher trigger voltages than the oxide breakdown voltage. Even when the trigger voltages of the ESD devices are lower than the oxide breakdown voltage, there is still no guarantee that the oxide can survive fast ESD events such as the CDM type of ESD events if the ESD devices are not triggered fast enough to shunt the ESD energy away from the MOS device.